1. Field of the Invention
This invention relates to invasive medical devices for injecting medications and therapeutic agents into the walls of blood vessels, body cavities, ducts, organs, tumors and the like. More particularly, the present invention relates to devices for concentrating the delivery of such medications and agents to the walls of the blood vessels, cavities and ducts.
2. State of the Art
Various vascular diseases involving vessel walls, such as arterial sclerosis, occlusive lesions, aneurysm or other weakening of the vessel wall, etc., may benefit from the application of medications directly to the affected area of the vessel wall. This may be done systemically by injecting medication into the vessel and then allowing the blood to carry the medication to the affected area. The problem with this approach is that high dosages of medication are required to ensure that some small portion reaches the affected area, and the high dosage may be harmful to other organs or body parts. Also, systemic application is generally not effective and quite expensive.
Another approach to treating diseases of vessel walls is to place a block before and after the affected area and then inject medications into that portion of the vessel between the two blocks. The problem with this approach is that blood flow is stopped for a certain amount of time and this, in itself, is dangerous; also, may not be able to stop the flow long enough for uptake of the medications.
Another prior art approach is to thread a catheter through the blood vessel to the affected area and then either supply the medication through the catheter to the affected area or supply the medication through a needle which itself is threaded through the catheter, pierce the vessel wall with the needle, and then supply the medication (see U.S. Pat. No. 5,354,279). The problem with simply supplying the medication via the catheter is that much of the medication is carried away in the blood and may adversely affect other organs.
An additional prior art approach to supplying medication to a vessel wall involves the use of an inflatable sleeve positioned adjacent the affected area, where the sleeve includes an annular cavity holding the medication. When the sleeve is inflated to expand outwardly, the medication held in the cavity is placed into contact with the vessel walls and released thereinto. The problem with this approach is that the blood vessel again is blocked for a time and thus a gradual therapeutic regimen is not possible.
Other approaches to delivering medication to vessel walls are disclosed in U.S. Pat. Nos. 5,681,281, 5,364,356, and 5,112,305.